Roof mounted automobile heat exchanger



Jan. 7, 1969 H. o. KIRKPATRICK 3,420,294

ROOF MOUNTED AUTOMOBILE HEAT EXCHANGER Filed Dec. 19 1966 Sheet of 2 s as 7- I04 55 I 92 INVENIOR Henry 0. KHkpGh'ICk Jan. 7, 1969 H. o.KIRKPATRICK 3,420,294

ROOF MOUNTED AUTOMOBILE HEAT EXCX'LANGER Filed Dec. 19. 1966 Sheet 3 0r2 INVENTOR Henry 0. Kirkpatrick ,WW Fig.8

United States Patent 3,420,294 ROOF MOUNTED AUTOMOBILE HEAT EXCHANGERHenry 0. Kirkpatrick, Dallas, Tex., assignor to Cummins Engine Company,Columbus, Ind., a corporation of Indiana Filed Dec. 19, 1966, Ser. No.602,994

US. Cl. 165-41 Int. Cl. F28b 1/06 6 Claims ABSTRACT OF THE DISCLOSUREThis invention relates to heat exchangers and more particularly to aheat exchanger for a refrigeration apparatus.

An object of this invention is to provide a new and improved heatexchanger through which air may be circulated to transfer heat betweenthe circulated air and a refrigerant fluid flowing through a coil of theheat exchanger.

Another object is to provide a heat exchanger of simple structure and ofrelatively small dimensions for a given heat transfer capability.

Another object of this invention is to provide a heat exchanger which ismountable on a vehicle through which air flow takes place due to themovement of the vehicle on which it is mounted, the heat exchangerhaving means for circulating air therethrough when the vehicle is notmoving or very slowly.

A further object is to provide a heat exchanger having a coil throughwhich a refrigerant fluid is circulated which provides for efficienttransfer of heat between the refrigerant fluid and air being circulatedthrough the heat exchanger.

Another object is to provide a heat exchanger having a coil assemblyarranged to constitute a section of a cylinder, the coil assembly havinga coil whose convolutions are spaced longitudinally of the cylinder andconvoluted heat transfer means between adjacent spaced sections of thecoil.

A still further object is to provide a heat exchanger of the typedescribed having end plates which close opposite ends of the coilassembly and air moving means disposed in the coil for moving airinwardly through opposite end portions of the coil assembly andoutwardly through a middle portion of the coil assembly.

Another object is to provide a coil assembly of the type describedhaving air circulation passages through substantially 340 degrees of acylinder whereby the circulation of air therethrough when the vehicle onwhich it is mounted is moving is faciliated due not only to ram effectbut also to the pressure differential created between the interior ofthe coil assembly and the exterior thereof due to the decrease inpressure above and rearwardly of the coil assembly.

Still another object is to provide a coil assembly wherein the flow Qfthe refrigerant through the coil of the coil assembly is in reversedirection to the flow of air through the end and middle portions of thecoil when the 3,429,294 Patented Jan. 7, 1969 air moving means is inoperation to provide an optimum substantially uniform temperaturegradient at all locations of the coil between the air circulatingthrough the coil assembly and the refrigerant fluid circulating throughthe coil.

Additional objects and advantages of the invention will be readilyapparent from the reading of the following description of a deviceconstructed in accordance with the invention, and reference to theaccompanying drawings thereof, wherein:

FIGURE 1 is a rear partly sectional view of a heat exchanger embodyingthe invention taken on line 11 of FIGURE 2;

FIGURE 2 is a partly sectional view taken on line 22 of FIGURE 1;

FIGURE 3 is a sectional view taken on line 3--3 of FIGURE 1;

FIGURE 4 is a perspective view of one of the end mount assemblies of theheat exchanger;

FIGURE 5 is a perspective view of a bottom closure plate of heatexchanger;

FIGURE 6 is a perspective view showing the end reinforcing plates of oneof the sections of the coil assembly;

FIGURE 7 is a fragmentary enlarged sectional view of the coil assembly;

FIGURE 8 is a fragmentary enlarged front view of the coil assembly; and,

FIGURE 9 is a fragmentary view of a modified form of the coil assembly.

Referring now particularly to FIGURES 1 through 8 of the drawings, theheat exchanger 15 embodying the invention is shown mounted on the roof Rof a vehicle for use as the condenser of a refrigerating apparatusemployed to cool and condense refrigerant fluid compressed by acompresser of the apparatus prior to its transmission to an evapartor ofthe apparatus disposed in a compartment of the vehicle wherein thecondensed refrigerant fluid evaporates and expands to cool suchcompartment.

The heat exchanger 15 includes a coil assembly 20 having a coil 21 whichconstitutes a section of approximately 340 degrees of a cylinder and aclosure plate 22 which extends between the longitudinal adjacent ends ofthe coil to close the gap of approximately 20 degrees therebetween. Thecoil may be formed of two sections 23 and 23a secured together inlongitudinal alignment. The section 23 has a flattened tube 25 dividedby longitudinal partitions 26 and 27 into three longitudinal passages 28which open at their inlet ends to the inner end of the tube inletcoupling 29 and at their outlet ends 29 to a similar outlet coupling 30.The tube is arranged in a plurality of arcuate convolutions about acentral longitudinal axis, the convolutions being defined by pairs ofadjacent parallel arcuate portions 31 and 32 connected at their forwardbottoms ends by arcuate front end portions 33 and at their rear ends byarcuate end portions 34. Convoluted heat exchanger fins or vane strips35 are disposed between adjacent parallel portions of the convolutionsof the tube with opposite bight portions of the strips being secured, asby welding, bonding or the like, in good heat conductive relationship tothe tube. The strips 35 impart great rigidity and strength to the coilsection and also provide for a good heat transfer between a refrigerantfluid which is circulated through the passages of the tube and air whichflows through the passages 38 defined by the strips 35 and the tube. Thepassages 38 extend radially relative to the central longitudinal axis ofthe coil assembly.

The inner and outer end strips 35s and 35t, respectively, of the coilsection 23 extend outwardly of the end arcuate portions of the tube andinner and outer arcuate end reinforcing plates 40 and 41, respectively,and are secured thereto. The reinforcing plates having inturned flanges42 to which opposite ends of the end strips are secured. The outerreinforcing plate 41 is provided with a plurality of threaded studs 44by means of which the reinforcing plate may be secured to an end plate45 which closes the outer end of the coil section 23.

The closure plate 22 of the coil assembly 20 has a bottom horizontalportion 48 over which extends, in tangential relationship, the forwardbottom end portion of the coil section 23 which is secured thereto bybolts 49 and suitable washers 50. The bolts extend through spacesbetween the end portions 33 of the tube convolutions and the ends of thestrips.

The outermost bolt also extends through a suitable aperture 51 in thehorizontal flange 52 of the angle bracket 53 of a mount assembly 54. Themount assembly is secured to the roof R of a vehicle by any suitable manner, as by bolts 55 which extend through suitable apertures of thehorizontal flange of the angle bracket. Suitable resilient spacers 56are interposed between the horizontal flange and the vehicle roof.

The rearwardly and upwardly extending portion 58 of the closure plateabuts the rear portion of the coil section and is rigidly secured thereby bolts 59 and washers 60, the bolts extending through the spacesbetween the end portions 34 of the tube and adjacent ends of the coolingstrips 35. The vertical flange 62 of the angle bracket of the end mountassembly 54 is rigidly secured to the end plate 45 in any suitablemanner, as by bolts 63, and to the outer reinforcing plate 41 of thecoil section 22 by means of the studs 44, which extend outwardly throughaligned apertures in the end plate and in a gasket 64 which isinterposed between the end plate and the reinforcing plate, and cap nuts65 threaded on the studs. The end plate may have a desired ornamentalconfiguration and be provided with an inwardly extending peripheralflange 66 which serves to conceal the angle bracket.

The coil section 23a and the mount assembly 54a are similar in structureto the coil section 23 and the mount assembly 54, and, accordingly,their elements have been provided with the same reference numerals, towhich the subscript a has been added, as the corresponding elements ofthe coil section 23 and the mount assembly 54.

The inner reinforcing plates 40 and 40a of the two coil sections 23 and23a, respectively, abut one another and are rigidly secured to oneanother in any suitable manner, as by bonding or the like so that thetwo coil sections are rigid with one another.

A plate 67 may be secured, as by screws, to the rear upwardly inclinedportion 58 of the closure plate to close the upper portions of the slots68 of the closure plate through which the couplings of the two coilsections extend. The plate 67 has slots 69 in which the upper portionsof the couplings are received. Suitable gaskets, not shown, may bedisposed about the couplings to prevent flow of air between thecouplings and the plates 22 and 67.

A motor 70 is mounted in the coil assembly by means of a motor mount 71whose bracket 72 has an arcuate middle portion rigidly secured, as bywelding, to an arcuate top motor clamp strap 75. The bracket hasupwardly and outwardly divergent arms 76 provided with downwardlyextending flanges 77 which are secured to the coil by means of bolts 78which extend through the passages 38 of the coil and suitable aperturesin the end flange. The bolts, of course, are provided with the usualwashers 79 and nuts 80. A brace bar 82 extends between and is rigidlysecured to the arms 76, as by welding. A bottom clamp strap 84 extendsbelow the motor and the two clamp straps are secured by bolts 86 whichextend through suitable apertures in their abutting end flanges. Theelectric cable 87 through whose conductors electric current is suppliedto the motor extends outwardly to an input circuit through an aperture88 of the closure plate. A grommet 89 prevents contact between theinsulation of the cable and the edges .Of the closure plate defining theaperture.

The drive shaft 90 of the motor has end portions extending outwardly ofthe motor to which are secured fans 91 and 91a. The fans are disposed atthe middles of the two coil sections and in alignment with the baffleplates 92 and 92a rigidly secured to the closure plate and which extendbetween the adjacent end portions of the coil sections to prevent airfrom bypassing the fans between the ends of the coil sections. Thepitches of the blades of the fans are such that when the motor isenergized, the fans draw air inwardly into the end passages through theradial passages 38 and 38a of the coil 21 at the end portions of thecoil and then into the middle passage from where the air flows outwardlythrough the radial passages at the middle portion of the coil.

Hot compressed gas from the compressor of a refrigeration apparatus isdelivered simultaneously by means of a branched conduit 97 and couplings98 and 98a connected to the inlet couplings 29 and 29a, respectively, ofthe coil 21, and thus to the inner inlet ends of the tubes 25 and 25a,respectively. The liquified and cooled refrigerant fluid is withdrawnfrom the outer ends of the tubes 25 and 25a by means of a branchedconduit 99 and couplings 100 and 100a which are connected to the othercouplings 30 and 30a, respectively.

The coil assembly and the end plates define a chamber 102 divided intoouter end passages 103 and 103a and a middle passage 104 by the fans andthe baflle plates. The middle passage of the chamber is approximatelytwice as long as the end passages so that the rate of outward flow ofthe air from the middle passage through the radial passages which openthereto is essentially equal to the rate of inward flow of air into theend passages through the radial pasages which open to the end passages.

In use, when the vehicle on which the condenser 20 is mounted istraveling forwardly, the air pressure along the front portion A of thecoil increases and simultaneously the pressure of the air along theupper and rear portions B and C, respectively, of the coil decreases.The air pressure forwardly of the coil is thus greater than the pressurewithin the passages 103, 103a and 104 of the coil assembly andsimultaneously the pressure rearwardly and upwardly of the coil is lessthan the pressure within these passages of the coil. As a result, due tothis pressure differential, as well as the ram effect created by theforward movement of the vehicle, air flows inwardly into the passages103, 103a and 104 of the coil assembly through the radial passages alongthe potrion A and flows outwardly from the passages 103, 103a and 104rearwardly through the radial passages along the rear portion C of thecoil and also upwardly through its radial passages along the portion B.Large volumes of air thus flow through the heat exchanger past verylarge areas of the tubes and of the cooling fins Or strips 35 and 35a sothat the air absorbs large amounts of heat from the hot compressedrefrigerant fluid flowing through the tubes as the air circulatesthrough the coil assembly.

When the vehicle is stopped for a short period of time, as for a traflicsignal light, it may not be necessary to energize the motor since someof the radial passages along the lower forward portion of the coil openupwardly into the passages 103, 103a and 104 of the heat exchanger andother radial passages at the top portion thereof open upwardly from thepassages and convective flow of air takes place through the heatexchanger as the air in the passages of the coil heats and rises.

If the vehicle remains stationary a long period of time, however, it isnecessary that forced circulation of air take place through the heatexchanger. The motor is then energized and, since the pitches of theblades of the two fans are reversed, as the fans are rotated in acounterclockwise manner, FIGURE 3, air is drawn inwardly through theradial passages of the portions of the coil located longitudinallyoutwardly of the fans into the end passages 103 and 103a, thence intothe middle passage 104 and then outwardly through the radial passages ofthe coil which open to the middle passage. Since the hot compressedrefrigerant fluid is introduced into the inner ends of the tubes 25 and25a of the coil 21 at the inlet couplings 29 and 29a and then flowsthrough the tubes to the outlet couplings 30 and 30a, the temperaturegradient between the refrigerant fluid flowing through the tubes at thelocation of the middle passage and the air flowing outwardly from themiddle passage of the coil through the radial passages which open to themiddle passage is substantially equal to the temperature gradientbetween the refrigerant fluid flowing through the portions of the tubesat the locations of the end passages and the air flowing inwardlythrough the radial passages which open into the end passages. It will beapparent that the air flowing inwardly into the end passages is coolerthan the air flowing outwardly from the middle passage since the air inflowing into the end passages is warmed due to the absorption thereby ofheat from the refrigerant fluid flowing through the tubes at thelocations of the end passages which has been somewhat cooled during itspassage through the portions of the tubes at the location of the middlepassage due to the absorption of air heat therefrom by the air flowingoutwardly through the radial passages which open to the middle passage.

It will now be seen that since the coil 21 is substantially tubular andextends transversely of the direction of movement of a vehicle on whichthe heat exchanger is mounted and since it is in substantially the formof a section of approximately 340 degrees of a cylinder, the coolingfins or strips and the tubes have very great areas of surface exposed tothe air which flows through the heat exchanger whether due to themovement of the vehicle on which the heat exchanger is mounted or due tothe operation of the fans.

It will further be seen that the heat exchanger may be of relativelysmall overall dimensions for a given rate or capacity of heat exchangebetween the fluid being circulated through its tubes and the air whichflows therethrough.

While the heat exchanger has been illustrated as being formed of twosections 23 and 23a, the heat exchanger may be formed of a coil having asingle tube whose middle rear arcuate portion is cut and the adjacentportion 34d and 342 thereof are connected to a single inlet conduit 29d,FIGURE 9, so that in effect the tube is separated into two sectionsextending from a middle vertical plane of such long coil and that therefrigerant fluid will then flow through such tube sections from theirinner ends outwardly to the outer ends thereof.

The foregoing description of the invention is explanatory only, andchanges in the details of the construction illustrated may be made bythose skilled in the art, within the scope of the appended claims,without departing from the spirit of the invention.

What is claimed and desired to be secured by Letters Patent is:

1. A heat exchanger. including: a tubular coil assembly, said coilassembly including a coil having a tube through which a heattransporting fluid may flow, said tube having convolutions, saidconvolutions being provided by parallel arcuate spaced portions of thetube and end connector portions connecting adjacent ends of adjacentparallel portions, and convoluted heat transfer strips disposed betweenadjacent parallel portions of the tube and providing with the tube aplurality of air passages which extend between the exterior and theinterior of said coil assembly; a pair of air moving means in said coilassembly dividing the interior of said coil assembly into a pair of endpassages and a middle passage; means in said coil for driving said airmoving means, said air moving means moving air inwardly into one of saidmiddle passage and said end passages through those of said air passageswhich open to one of said middle passage and said end passages andmoving air outwardly from the other of said middle passage and said endpassages through those of said air passages which open to said other ofsaid middle passage and said end passages; and means for closing outerends of said end passages, said tube and said convoluted strips of saidcoil lying in a section of a cylindrical plane of at least 180 degrees;said coil assembly including a closure plate closing the space betweenadjacent ends of said coil whereby air may move into and out of said endand middle passages only through said air passages.

2. The heat exchanger of claim 1, and means for introducing heattransporting fluid into said tube at a midpoint thereof and forwithdrawing fluid from said tube at opposite ends thereof.

3. The heat exchanger of claim 2, and means for mounting said heatexchanger on a vehicle in position wherein the axis of said cylindricalplane extends transversely to the direction of forward movement of thevehicle and forward movement thereof will cause air to flow inwardlyinto the end and middle passages through air passages at the frontpotrion of said coil assembly and outwardly from the end and middlepassages through air passages at the rear and upper portions of saidcoil assembly.

4. A heat exchanger adapted to be mounted on a vehicle for use as acondenser of a refrigerator apparatus, said heat exchanger including: asubstantially tubular, elongated coil assembly having an elongatedchamber closed at its ends and extending transversely to the directionof movement of a vehicle on which the heat exchanger is mounted, saidcoil assembly including a convoluted tube through which refrigerantfluid may flow, and a plurality of heat transfer fins betweenconvolutions of the tube, said tube and said fins constituting anarcuate coil and said coil being in the form of a section of a cylindergreater than 180 degrees, said coil having transversely extending sides,said coil assembly including a closure plate extending between saidspaced sides and closing the space therebetween, said tube and said finsdefining a plurality of spaced air passages opening from such chamberforwardly at the front portion of the coil assembly, upwardly at theupper portion of the assembly and rearwardly at the rear portion of thecoil assembly whereby when a vehicle on which the heat exchanger ismounted is moving forwardly, air flows inwardly into said chamberthrough air passages of said assembly at the front portion of saidassembly and outwardly from the interior of said assembly through airpassages along another portion of said assembly and air moving means formoving air inwardly into the interior of said assembly through airpassages along one portion of said assembly and outwardly from theinterior of said assembly through air passages along another portion ofsaid assembly.

5. The heat exchanger of claim 4, and end mount assemblies secured tosaid coil assembly at opposite ends thereof for mounting said heatexchanger on a vehicle.

6. The heat exchanger of claim 5, wherein said air moving meanscomprises a pair of spaced fans in said chamber for moving aid inopposite transverse directions in said chamber.

References Cited UNITED STATES PATENTS 1,589,412 6/1926 Mitchell 1252,162,512 6/1939 McPherson et al. 62244 XR 2,405,411 8/1946 Dybvig165125 XR 2,610,484 9/1952 Lange 165-125 XR 2,856,162 10/1958 Adams165125 2,977,774 4/ 1961 Ferris 62243 XR ROBERT A. OLEARY, PrimaryExaminer.

MANUEL A. ANTONAKAS, Assistant Examiner.

US. 01. X.R.

